10-4 means 'message received / understood' — an acknowledgment, not agreement. To confirm you will comply, military and aviation radio uses WILCO ('will comply') instead.

What does 10-20 mean?

10-20 means location — 'what's your 20?' asks where you are. It is one of the few 10-codes with a near-universal meaning across US agencies.

Are police 10-codes the same everywhere?

No. 10-codes vary between agencies — 10-13 can mean 'weather report' or 'officer needs help' depending on the department. After interoperability failures on 9/11, many US agencies switched to plain language.

What does Code 3 mean?

In most US and NZ agencies, Code 3 means respond immediately with lights and siren. Code 1 is routine response and Code 2 is urgent without siren, though exact definitions vary by department.

What does Code 4 mean?

Code 4 means 'no further assistance needed — situation under control'. Dispatchers broadcast it to release other units still responding to the call.

What is the difference between ROGER and WILCO?

ROGER means 'I received your message'; WILCO means 'received and I will comply'. Saying 'roger wilco' is incorrect — WILCO already includes receipt.

Police 10-Codes, Military Code Words and Radio Prowords

Police 10-codes are numeric brevity codes (10-4 = message received) used on law-enforcement radio; NATO prowords like ROGER and WILCO do the same job on military nets. Codes vary by agency — always confirm local usage.

Police 10-Codes

10-1

Signal weak

10-2

Signal good

10-3

Stop transmitting

10-4

Acknowledged / OK

Most widely known code

10-5

Relay message

10-6

Busy — stand by

10-7

Out of service

10-8

In service / Available

10-9

Repeat last message

10-10

Off duty

10-13

Weather / road conditions

10-20

Location

Most common field use

10-21

Call by telephone

10-22

Disregard / Cancel

10-23

Arrived at scene

10-26

Detaining suspect

10-27

Driver license check

10-28

Vehicle registration check

10-29

Check for warrants

10-31

Crime in progress

10-32

Person with gun

Armed subject

10-33

Emergency all units stand by

10-36

Correct time

Time check

10-38

Traffic stop

10-39

Urgent lights and siren

10-40

Silent run

Covert approach

10-50

Accident

Traffic collision

10-52

Ambulance needed

10-55

Suspected DUI

10-57

Hit and run

10-70

Fire alarm

10-76

En route

Responding

10-77

ETA

Estimated arrival

10-78

Need assistance

Officer needs backup

10-79

Notify coroner

Death at scene

10-80

Chase in progress

Vehicle pursuit

10-95

Prisoner in custody

10-98

Finished available

10-99

Wanted / stolen

High priority

Status Codes

Code 1

Routine no rush

Code 2

Urgent no siren

Code 3

Emergency lights and siren

Code 4

No further assistance

Code 5

Stakeout stay away

Plainclothes

Code 6

Out of car investigation

Code 7

Meal break

Code 9

Jail break

Escape in progress

Code 10

Bomb threat

Code 33

Emergency clear the air

Code 37

Subject wanted

Code 99

Officer needs help

Officer down

Penal / Incident Codes

187

Homicide

CA Penal Code

211

Robbery

245

Assault with deadly weapon

ADW

261

Rape

390

Drunk in public

415

Disturbing the peace

451

Arson

459

Burglary

484

Petty theft

487

Grand theft

502

DUI

503

Vehicle theft

Grand theft auto

594

Vandalism

602

Trespassing

647

Disorderly conduct

NATO Prowords

Proword	Meaning
BREAK	Separates long messages without ending transmission
COPY	Message received and understood
CORRECTION	Error in previous transmission — correction follows
DO NOT ANSWER	Do not reply to this message
I SAY AGAIN	Intentionally repeating previous transmission
MORE TO FOLLOW	Additional information coming
NEGATIVE	No / Disagreement / Request denied
OUT	End of conversation — initiating station only
OVER	End of transmission — reply expected
READ BACK	Repeat this transmission verbatim back to me
RELAY TO	Forward to named station
ROGER	Received and understood your last transmission
SAY AGAIN	Repeat your last transmission
SILENCE x3	All stations cease transmission immediately
SILENCE LIFTED	Normal communication may resume
VERIFY	Check and confirm the information
WILCO	Will comply — implies Roger, never use together

Military Tactical Phrases

Oscar Mike

On the move

Unit relocating

Charlie Mike

Continue mission

Resume after interruption

Lima Charlie

Loud and clear 5x5

Signal quality

Bravo Zulu

Well done

NATO praise signal

Tango Yankee

Thank you

Radio courtesy

November Golf

No good

Negative assessment

Tango Delta

Target down

Engagement report

Whiskey Pete

White phosphorous

Munition type

40 Mike Mike

40mm grenade / M203

Weapons reference

Romeo Foxtrot

Radio frequency

Comms context

Military Acronyms

FUBAR

F***ed Up Beyond All Recognition

WWII origin

SNAFU

Situation Normal: All F***ed Up

WWII, now mainstream

BOHICA

Bend Over Here It Comes Again

Dark humour

TARFU

Things Are Really F***ed Up

Above SNAFU

AWOL

Absent Without Leave

Legal military status

FOB

Forward Operating Base

Tactical outpost

ROE

Rules of Engagement

Legal framework for force

SITREP

Situation Report

Command update format

Critical Radio Rules

NEVER say "REPEAT" on radio. It is an artillery command meaning fire again. Always say SAY AGAIN.

NEVER say WILCO and ROGER together. WILCO already implies Roger.

NZ Police Notes

NZ Police use a modified 10-code set. Common NZ codes: 10-1 Signal weak · 10-4 Acknowledged · 10-20 Location · 10-76 En route.

Codes Reference